And furthermore, what would be a better design for this type of structure?
It's easy to design a better system than dailies, pump out infinite amounts of content, it's just not feasible to pull off. Some people want to spend more time in the game than others, maybe even every day, and we want to make sure they have something to do. While we'd love for that to be fresh and unique content every time, it's simply not feasible. Thus, dailies. Give people something to do each time they log in (if they choose to do so every day).
Not to toot the Mists of Pandaria horn too hard, but I think our general zone design, daily, and scenario approach is pretty solid. Part of what makes dailies a bit tedious, aside from being tedious, is the rewards are desired but may not always quite fit the time investment. I see quite a bit of that being solved and making sure if you're logging in to do some dailies or scenarios, you feel like you made a good chunk of progress toward advancing your character.